The present invention relates to an improved process for the hydroalkylation of mononuclear aromatic hydrocarbons, namely benzene and analogs thereof, to form cycloalkylaromatics. Many patents have recently issued in the field of hydroalkylation of mononuclear aromatics. See, for example, U.S. Pat. No. 3,760,019, U.S. Pat. No. 3,784,617, U.S. Pat. No. 3,784,618, U.S. Pat. No. 3,829,514, U.S. Pat. No. 3,829,515, U.S. Pat. No. 3,829,516 and U.S. Pat. No. 3,829,517. In the processes disclosed in these patents, benzene or analog is contacted with a catalyst which is normally composed of a Group VIII transition metal supported on a suitable carrier, the catalyst optionally containing tungsten. Many different supports are disclosed as useful including silica-alumina, zeolite and alumina. Specific Group VIII transition metals disclosed to be useful are cobalt, nickel, ruthenium, rhodium, palladium, iridium and platinum.
Although processes disclosed in the foregoing patents are capable of effecting hydroalkylation of benzene and analogs to the corresponding cycloalkylaromatic compounds, they are disadvantageous in that they are unable to provide the desired cycloalkylaromatic product compounds with high yields and high selectivities. Moreover, in many processes it is necessary to subject the catalyst to be used to an activation pre-treatment by reducing the catalyst with H.sub.2 prior to beginning the hydroalkylation reaction. In still other processes, it is necessary to carry out the hydroalkylation reaction in stages, the total amount of hydrogen necessary to effect hydroalkylation being added to the reaction system in stepped additions.
Accordingly, it is an object of the present invention to provide an improved process for the catalytic hydroalkylation of benzene and analogs to the corresponding cycloalkylaromatic compounds which produces the desired product compounds in higher yield and with higher selectivities than processes known prior to the present invention.
It is a further object of the present invention to provide a hydroalkylation process of the type described above which can be carried out either in batch mode or continuously in a single stage operation, i.e. a process which does not require stepped addition of reactants.
It is still another object of the present invention to provide a hydroalkylation process in which the catalyst to be used can be employed directly after calcination, H.sub.2 reduction of the catalyst prior to use being unnecessary.